Hydrogenation and dehydrogenation catalyst, and methods of making and using the same

ABSTRACT

The present application discloses complexes useful as catalysts for organic chemical synthesis including hydrogenation and dehydrogenation of unsaturated compounds or dehydrogenation of substrates. The range of hydrogenation substrate compounds includes esters, lactones, oils and fats, resulting in alcohols, diols, and triols as reaction products. The catalysts of current application can be used to catalyze a hydrogenation reaction under solvent free conditions. The present catalysts also allow the hydrogenation to proceed without added base, and it can be used in place of the conventional reduction methods employing hydrides of the main-group elements. Furthermore, the catalysts of the present application can catalyze a dehydrogenation reaction under homogenous and/or acceptorless conditions. As such, the catalysts provided herein can be useful in substantially reducing cost and improving the environmental profile of manufacturing processes for variety of chemicals.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Divisional application of a non-provisional application havingU.S. patent application Ser. No. 14/239,179 filed on May 27, 2014, theNational Phase application of International Application No.PCT/CA2012/050571 filed on Aug. 20, 2012, U.S. Provisional ApplicationNo. 61/524,815 filed on Aug. 18, 2011, and U.S. Provisional ApplicationNo. 61/593,840 filed on Feb. 1, 2012, the contents of which are allincorporated herein by reference.

FIELD OF THE INVENTION

The present invention pertains to catalysts. More specifically, thepresent invention pertains to catalysts useful in hydrogenation anddehydrogenation reactions.

INTRODUCTION

Reduction of esters is one of the most fundamental organic reactions andis useful for synthesis of a variety of useful organic alcohols. Thereduction of esters is typically accomplished using main-group hydridereagents, such as LiAlH₄, or using molecular hydrogen. The use ofhydride reducing reagents is inconvenient and expensive, particularly ona large scale; furthermore, this approach generates large amounts ofchemical waste. The hydride reduction method can also be dangerouslyexothermic at the stage of quenching and it can be difficult to control.The catalytic reduction of esters under hydrogen gas is, in allrespects, a very attractive ‘green’ alternative to the classical hydridereduction.

A key aspect of the ester reduction with molecular hydrogen is thecatalytic system utilized in the process that can rapidly bind and splitmolecular hydrogen to give a transition-metal hydride. The developmentof highly efficient and useful catalysts and catalytic systems forhydrogenation of lactones, esters, oils, and fats is an important needin chemistry. Particularly, developing hydrogenation processes operatingin the temperature range of 20 to 100° C. using less than 1000 ppm (0.1mol %) catalyst under relatively low H₂ pressure (1-50 bar) is highlydesirable. Among the few catalysts and catalytic systems capable ofconverting esters and lactones into alcohols and diols under hydrogengas, the presently most useful and efficient are complexes of transitionmetals, such as ruthenium, with bidentate phosphine-amine ortetradentate phosphine-imine ligands as described in Publication No. US2010/0280273 A1 and in Angew. Chem. Int. Ed. 2007, 46, 7473,incorporated herein by reference. Typical ruthenium catalyst loadings of500-1000 ppm (0.05-0.1 mol %) are used, however, the major drawback ofsuch methods is the need for a large amounts of base (5-10 mol %) suchas NaOMe, thereby reducing the product selectivity and generating largeamounts of chemical waste due to the need for product neutralization andextensive purification. Furthermore, no hydrogenation of naturallyoccurring esters, e.g. plant oils such as olive oil, to give unsaturatedfatty alcohols was reported with the ruthenium catalysts. Fatty alcoholsbehave as nonionic surfactants due to their amphiphilic nature. Theyfind use as emulsifiers, emollients and thickeners in the cosmetics andfood industries, and as industrial solvents. Fatty alcohols are alsovery useful in the production of detergents and surfactants, and theyhave a potential in the production of biodiesel.

The development of green chemical processes and the use of biomass forhydrogen production have attracted much attention in recent years.Significant progress in dehydrogenation of bio-alcohols (chieflyethanol) has been achieved with heterogeneous catalysts, however, at thecost of using drastic reaction conditions, such as high temperature(>200° C.) and pressure. Therefore, designing well-defined homogeneouscatalysts for the dehydrogenation of alcohols under mild conditionsrepresents an important scientific and practical goal.

There has been little progress in the area of acceptorlessdehydrogenation of primary alcohols since Cole-Hamilton and co-workersdemonstrated dehydrogenation of ethanol catalyzed by [RuH₂(N₂)(PPh₃)₃],where an excess of NaOH, high temperature (150° C.), and an intenselight source were needed to achieve TOF=210 h⁻¹, after 2 h (D. Morton,D. J. Cole-Hamilton, I. D. Utuk, M. Paneque-Sosa, M. Lopez-Poveda, J.Chem. Soc. Dalton Trans. 1989, 489; D. Morton, D. Cole-Hamilton, J.Chem. Soc. Chem. Commun. 1988, 1154; and D. Morton, D. J. Cole-Hamilton,J. Chem. Soc. Chem. Commun. 1987, 248). In recent years, several newhomogeneous catalysts for acceptorless dehydrogenative coupling ofprimary alcohols have been developed and studied, such as the systemspublished by Milstein and co-workers (for a review see: D. Milstein,Top. Catal. 2010, 53, 915). However, all these new catalysts areinactive at temperatures below 100° C., for example, for convertingethanol and propanol to hydrogen and ethyl acetate and propylpropionate, respectively.

Therefore, there remains a need for efficient metal catalysts for thehydrogenation of esters, lactones, and fats and oils derived fromnatural sources, which could operate under base-free conditions andusing relatively low reaction temperature and hydrogen pressure. Therealso remains a need for catalysts capable of efficient alcoholdehydrogenation under mild, and preferably neutral, reaction conditions,for environmentally benign production of esters and lactones fromalcohols and diols, respectively, accompanied by formation of hydrogengas.

The above information is provided for the purpose of making knowninformation believed by the applicant to be of possible relevance to thepresent invention. No admission is necessarily intended, nor should beconstrued, that any of the preceding information constitutes prior artagainst the present invention.

BRIEF DESCRIPTION OF THE FIGURES

For a better understanding of the present invention, as well as otheraspects and further features thereof, reference is made to the followingdescription which is to be used in conjunction with the accompanyingdrawings, where:

FIG. 1 is an ORTEP diagram for complex 1, thermal ellipsoids are at 50%probability (the hydrogen atoms are omitted for clarity); and

FIG. 2 is an ORTEP diagram for complex 2, thermal ellipsoids are at 50%probability (the hydrogen atoms are omitted for clarity).

FIG. 3 is an ORTEP diagram for complex 7, thermal ellipsoids are at 50%probability (the hydrogen atoms except for NH are omitted for clarity).

DESCRIPTION OF THE INVENTION

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs.

As used in the specification and claims, the singular forms “a”, “an”and “the” include plural references unless the context clearly dictatesotherwise.

The term “comprising” as used herein will be understood to mean that thelist following is non-exhaustive and may or may not include any otheradditional suitable items, for example one or more further feature(s),component(s) and/or ingredient(s) as appropriate.

As used herein, “heteroatom” refers to non-hydrogen and non-carbonatoms, such as, for example, O, S, and N.

As used herein, “alkyl” means a hydrocarbon moiety that consists solelyof single-bonded carbon and hydrogen atoms, for example a methyl orethyl group.

As used herein, “alkenyl” means a hydrocarbon moiety that is linear,branched or cyclic and comprises at least one carbon to carbon doublebond. “Alkynyl” means a hydrocarbon moiety that is linear, branched orcyclic and comprises at least one carbon to carbon triple bond. “Aryl”means a moiety including a substituted or unsubstituted aromatic ring,including heteroaryl moieties and moieties with more than one conjugatedaromatic ring; optionally it may also include one or more non-aromaticring. “C₅ to C₈ Aryl” means a moiety including a substituted orunsubstituted aromatic ring having from 5 to 8 carbon atoms in one ormore conjugated aromatic rings. Examples of aryl moieties includephenyl.

“Heteroaryl” means a moiety including a substituted or unsubstitutedaromatic ring having from 4 to 8 carbon atoms and at least oneheteroatom in one or more conjugated aromatic rings. As used herein,“heteroatom” refers to non-carbon and non-hydrogen atoms, such as, forexample, O, S, and N. Examples of heteroaryl moieties include pyridyl,furanyl and thienyl.

“Alkylene” means a divalent alkyl radical, e.g., —C_(f)H_(2f)— wherein fis an integer. “Alkenylene” means a divalent alkenyl radical, e.g.,—CHCH—.

“Substituted” means having one or more substituent moieties whosepresence does not interfere with the desired reaction. Examples ofsubstituents include alkyl, alkenyl, alkynyl, aryl, aryl-halide,heteroaryl, cycloalkyl (non-aromatic ring), Si(alkyl)₃, Si(alkoxy)₃,halo, alkoxyl, amino, alkylamino, alkenylamino, amide, amidine,hydroxyl, thioether, alkylcarbonyl, alkylcarbonyloxy, arylcarbonyloxy,alkoxycarbonyloxy, aryloxycarbonyloxy, carbonate, alkoxycarbonyl,aminocarbonyl, alkylthiocarbonyl, phosphate, phosphate ester,phosphonato, phosphinato, cyano, acylamino, imino, sulfhydryl,alkylthio, arylthio, thiocarboxylate, dithiocarboxylate, sulfate,sulfato, sulfonate, sulfamoyl, sulfonamide, nitro, nitrile, azido,heterocyclyl, ether, ester, silicon-containing moieties, thioester, or acombination thereof. The substituents may themselves be substituted. Forinstance, an amino substituent may itself be mono or independentlydisubstituted by further substituents defined above, such as alkyl,alkenyl, alkynyl, aryl, aryl-halide and heteroaryl cycloalkyl(non-aromatic ring).

As used herein, the term “μ^(Y)” is used to indicate that a ligand isfunctioning as a bridging ligand, where a single atom bridges two metalatoms. The superscript “Y” denotes the atom bridging the two metalatoms. For example, the term “μ^(N)” is used to indicate that a ligand(or ligands) in a complex includes a nitrogen atom that bridges twometal atoms.

The present application provides a catalyst that is useful in a processof catalytic hydrogenation (reduction). The process is useful inhydrogenation of, for example, C₃-C_(n) (n=4-200) substrates possessingone or more ester or lactone groups to afford the corresponding alcohol,diol, or triol products. Thus, the present application further providesa practical reduction method that can be used in place of the main-grouphydride reduction to obtain alcohols, diols, or triols in a simple,efficient, and “green” fashion, preferably using base-free reactionconditions. The catalyst of the present application is also useful in aprocess of catalytic dehydrogenation, which can be a homogeneousdehydrogenation process.

Catalyst

The processes described herein are carried out in the presence of atransition metal complex having a tridentate ligand LNN′.

In accordance with one aspect, there is provided a tridentate ligandLNN′ comprising, in sequence, one phosphorus, sulfur, nitrogen or carbongroup L, one amino or imino group N, and one heterocycle group N′.

In accordance with one embodiment, there is provided a compound ofFormula I

wherein

L is a phosphine (PR¹R²), a sulfide (SR¹), or a carbene group (CR¹R²);

each Y is independently a C, N or S atom, wherein at least two Y's areC;

the dotted lines simultaneously or independently represent single ordouble bonds;

R¹ and R² are each independently H, or a C₁-C₂₀ linear alkyl, a C₃-C₂₀branched alkyl, a C₃-C₈ cycloalkyl, a C₂-C₈ alkenyl, a C₅-C₂₀ aryl, eachof which may be optionally substituted; or when taken together, R¹ andR² can together with L to which they are bound form a saturated orpartially saturated ring;

R³ and R⁴ are each independently H, or a C₁-C₈ linear alkyl, a C₃-C₈branched alkyl, a C₃-C₈ cyclic alkyl, a C₂-C₈ alkenyl, a C₅-C₈ aryl,each of which may be optionally substituted; or R³ and R⁴ can jointogether to form a saturated heterocycle;

R⁵ is H, a linear C₁-C₈ alkyl, a branched C₃-C₈ alkyl, a cyclic C₃-C₈alkyl, a C₂-C₈ alkenyl, or a C₅-C₈ aryl, each of which can be optionallysubstituted; or R⁵ and R⁴ can join together to form a saturatedheterocycle;

each X is independently H, a linear C₁-C₈ alkyl, a branched C₃-C₈ alkyl,a cyclic C₃-C₈ alkyl, a C₂-C₈ alkenyl, or a C₅-C₈ aryl, each of whichcan be optionally substituted, or OR, F, Cl, Br, I or NR₂; or when takentogether, two of the X groups can together form an optionallysubstituted, saturated, partially saturated, aromatic or heteroaromaticring;

R is H, a C₁-C₂₀ linear alkyl, a C₃-C₂₀ branched alkyl, a C₃-C₈cycloalkyl, a C₂-C₈ alkenyl, or a C₅-C₈ aryl, each of which may beoptionally substituted;

each n and m is independently 1 or 2;

k is 1 or 2;

and

z is 0 or 1.

In accordance with one embodiment, R³ and R⁴ are each independently H,or C₁-C₈ linear alkyl, C₃-C₈ branched alkyl, cyclic alkyl C₃-C₈, C₁-C₈alkenyl, C₅-C₈ aryl, each of which may be optionally substituted, or ORor NR₂; and R⁵ is H, a linear C₁-C₈ alkyl, branched C₃-C₈ alkyl, cyclicC₃-C₈ alkyl, C₃-C₈ alkenyl, or C₅-C₈ aryl, each of which can beoptionally substituted, or OR or NR₂. In one preferred embodiment, R⁴and R⁵ are both H.

In accordance with another embodiment, each Y is C. In accordance withanother embodiment, k is 2, and each X is H. In accordance with onepreferred embodiment, L is a phosphene.

In accordance with one embodiment, the compound of Formula I is

In accordance with another aspect, there is provided a complex ofFormula II or III[M(LNN′)Z_(a)]  (II)μ^(N)[M(LNN′)Z_(a)]₂  (III)wherein:

each Z is independently a hydrogen or halogen atom, a C₁-C₆ alkyl, ahydroxyl, or a C₁-C₆ alkoxy, a nitrosyl (NO) group, CO, CNR, or PR₃,wherein R is an alkyl or an aryl, PMe₃ or PPh₃;

M is a transition metal; and

each LNN′ is a coordinated ligand that is a compound of any one ofclaims 1-7.

In accordance with one embodiment, M is a group 7 metal, a group 8 metalor a group 9 metal. In accordance with one preferred embodiment, M is Ruor Os.

In accordance with another embodiment, the complex comprises the ligandLNN′, wherein LNN′ is

In accordance with another embodiment, the complex has the structure of

wherein M is as defined above.

In one preferred embodiment, the complex has the structure of any one of

In accordance with another aspect, there is provided a process fordehydrogenation of a substrate comprising treating the substrate with acatalytic amount of a complex as described. In one embodiment, thesubstrate is a compound of Formula IV

wherein R⁹ is a C₁₋₂₀ linear alkyl, a C₃₋₂₀ branched alkyl, a C₃₋₂₀cycloalkyl, or an aryl, any of which may be optionally substituted.

In accordance with another aspect, there is provided a tridentate ligandLNN′ having formula I, R⁴ is H, a substituted or unsubstituted linear,branched or cyclic C₃-C₈ alkyl or alkenyl, a substituted or anunsubstituted C₅-C₈ aromatic group, and R⁵ is a substituted orunsubstituted linear, branched or cyclic C₃-C₈ alkyl or alkenyl, asubstituted or unsubstituted C₅-C₈ aryl.

In one embodiment, the heterocycle group N′ of Formula I, wherein k is 1or 2, the nitrogen heterocycle N′ is optionally substituted and containscarbon, nitrogen, oxygen, or sulfur atoms Y. One preferred example ofthe heterocycle N′ is the C₂-pyridyl group, C₅H₄N.

In another particular embodiment, L is an N-heterocyclic carbene. Inanother particular embodiment, L is a phosphene.

Some specific examples of tridentate ligands LNN′ are:

The tridentate ligand LNN′ described above can be synthesized usingstandard procedures. For example, the ligand can be obtained bycondensation of optionally substituted 2-pycolyl aldehyde (2-CHO-Py)with an aminophosphine or an optionally substituted thioamine. Reductionof the imine product by NaBH₄, Al(tBu)₂H or any other reducing reagentswell known in the state of the art will lead to the LNN′ ligand ofFormula I.

The presently described tridentate ligands are of relatively low cost toproduce. The reduced cost is at least partially the result of the use ofless expensive chemicals as well as surprisingly high efficiency ofligand synthesis. Production of the present ligands are already order ofmagnitude less expensive than other examples of tridentate ligands usedin catalyst complexes in the literature.

According to another aspect, there are provided complexes of the generalFormulae II and III:[M(LNN′)Z_(a)]  IIμ^(N)[M(LNN′)Z_(a)]₂  IIIwherein LNN′ is the tridentate ligand of Formula I and a equals 2 or 3.Each Z represents simultaneously or independently a hydrogen or halogenatom, a C₁-C₆ alkyl radical, a hydroxyl group, or a C₁-C₆ alkoxyradical, a nitrosyl (NO) group, CO, CNR (R=Alkyl, Aryl), PMe₃ or PPh₃,and M is a transition metal. The complexes as presently described mayexist in both neutral and cationic forms.

In accordance with one embodiment, the transition metal M is preferablya metal from groups 7 (manganese group), 8 (iron group), and 9 (cobaltgroup). In one preferred embodiment, the transition metal is Ru or Os.

In one embodiment, the complex of Formula II can be prepared by reactionof the LNN′ ligand of Formula I with a metal precursor, such as thosewell known in the state of the art. Preferably, the metal precursor is aruthenium or osmium compound, including, for example, the followingformulae: RuHCl(CO)(AsPh₃)₃, RuCl₂(CO)(AsPh₃)₃, RuHCl(CO)(PPh₃)₃.RuCl₂(CO)(PPh₃)₃, OsHCl(CO)(AsPh₃)₃, OsCl₂(CO)(AsPh₃)₃, OsHCl(CO)(PPh₃),OsCl₂(CO)(PPh₃)₃, [RuCl₂(p-cymene)]₂, [OsCl₂(p-cymene)]₂,RuCl₂(CO)(p-cymene), OsCl₂(CO)(p-cymene), RuCl₂(CO)(DMF)(PPh₃)₂,[IrCl(COD)]₂, [IrCl(COE)₂]₂, IrHCl₂(PPh₃)₃, IrH₂Cl(PPh₃)₃,IrHCl₂(AsPh₃)₃, or IrH₂Cl(AsPh₃)₃. The reactions can be conducted invarious organic solvents, such as, but not limited to, toluene, xylene,benzene, diglyme, DMF or DME.

In accordance with another embodiment, transformation of a complexes ofFormula II to a complex of Formula III can be achieved using a base.Non-limiting examples of suitable bases include group I salts (such asLi, Na, K) of alkoxides, such as t-butoxide, and amides, such asN(TMS)₂. One specific examples of an acceptable base is potassiumt-butoxide. In certain, non-limiting, examples, the base has a pKa>11.Additional non-limiting examples of suitable bases are group I salts orammonium of hydroxides, alcoholates, alkaline carbonates, amides,siliconates, hydrides, borohydrides, aluminum hydrides, where the groupI salt is Li, Na, K, or ammonium salts of the formula NR₄, and R isalkyl, aryl or H.

Complexes of Formulae II and III can be prepared prior to hydrogenationor in situ using above bases. Preparation of complexes of Formula II andIII can be performed in various solvents, such as, but not limited toTHF, Et₂O, toluene, benzene, diglyme, DMF or DME or any otherappropriate solvents known to the person skilled in the art.

Structures of exemplary complexes 1-9 are shown below:

In another aspect, there is provided a process for making ethyl acetatecomprising treating ethanol with a catalytic amount of a complex asdescribed herein. In one embodiment, the process of is a homogeneousprocess. In another embodiment, the process does not require a hydrogenacceptor.

Hydrogenation Process

The present application additionally provides a catalytic hydrogenationprocess. The catalyst complexes of Formulae II and III described above,have been found to show high selectivity toward reduction of the estergroups in the presence of C═C double bonds. This provides a useful wayof deriving unsaturated alcohols from natural products such as, but notlimited to, olive or canola oils, under mild reduction conditions.

In one embodiment, there is provided a process for hydrogenation ofesters using metal catalysts based on the LNN′ ligand of Formula I.According to specific embodiment, the substrates are compounds of thefollowing formulae:

The term “substrate”, as used herein and as commonly understood, refersto the reactant that will be converted to a product during a catalyticreaction. Groups G1 and G2, simultaneously or independently, represent alinear, branched C₁-C₄₀ or cyclic C₃-C₄₀ alkyl, alkenyl or aromaticgroup, optionally substituted. Also, one may cite a situation when G1and G2 together form a C₄-C₄₀ saturated or an unsaturated radical. Thesubstrate of the hydrogenation reaction can be any organic compoundcontaining one, or more than one, carboalkoxy group. In this respect,natural fats such as olive, canola, corn, peanut, palm and other plantoils are useful substrates that can be reduced to form a mixture ofalcohols.

The reduction or hydrogenation reaction proceeds, generally, accordingto the one of the reactions scheme below:

wherein G₁ and G₂ are independently selected from any optionallysubstituted hydrocarbon group. For clarity, where multiple substituentsG₁ occur in the same molecule, it is understood that each of thesesubstituents can be a different optionally substituted hydrocarbon.

When the substrate is a monoester or a lactone, the products arealcohols or a diol, respectively. The naturally occurring triglycerides,oils and fats, can be reduced to glycerol and the corresponding fattyalcohols.

According to one embodiment of the invention, the process of catalyticreduction of esters implies the usage of at least one of the metalcomplexes 1 or 2, hydrogen pressure, and optionally a base and asolvent. The base may be necessary in those cases when the metalcatalyst 1 contains one or more halogen atoms bonded to the metal. Thetreatment with base can be done prior to the reduction or in situ byadding base to the reaction mixture during hydrogenation. The catalystsand pre-catalysts of this invention can be used in a wide range ofconcentration, preferably between 10-1000 ppm, and the loadings of 500ppm or less are particularly preferred. The preferred amount of thecatalyst will depend, as it is known to the person skilled in the art,on the type of the substrate, and increasing the catalyst loading shouldresult in faster hydrogenation. The temperature at which thehydrogenation can be carried out is comprised between 0° C. and 150° C.,more preferably in the range between 50° C. and 100° C. and, as it isknown to the person skilled in the art, the reaction rate will increasewith increase of the reaction temperature. The hydrogenation reactionneeds a pressure of H₂ gas and should be performed in a suitablepressure vessel. The surface area of the reactor as well as the hydrogenpressure, as it is known to the person skilled in the art, can greatlyinfluence the reaction rate. The greater are the hydrogen pressure andthe surface area of the reactor, the faster is the hydrogenationreaction rate. One may cite the hydrogen pressure in range of 10-200Bar. Again, the person skilled in the art is well able to adjust thepressure as a function of the catalyst load and of the dilution of thesubstrate in the solvent. As examples, one can cite typical pressures of5 to 50 bar (5 to 50×10 Pa).

It should be well understood, however, that the catalyst complexesdescribed herein are also useful in catalyzing hydrogenation ofsubstrates including functional groups other than esters. The tablebelow provides a non-limiting list of substrates and correspondingproducts that can be formed from a catalytic hydrogenation reactionusing a catalyst of Formula II or III.

Hydrogenation Substrate Product aldehyde alcohol ketone alcohol esteralcohol carboxylic acid alcohol ketene alcohol enol alcohol epoxidealcohol aldimine amine ketimine amine ketene-imine amine nitrile amineaziridine amine nitro amine diazo amine isocyanide amine enamine aminelactone diol amide amine + alcohol aminoboranes amine-borane borazineamine-borane olefin alkane acetylene alkane allene alkane

Dehydrogenation Reaction

The present application further provides a process of catalyticdehydrogenation using the catalyst complexes of Formulae II and III. Forexample, this catalyst or precatalyst is suitable for dehydrogenation ofC₂-C_(n) (n=4-200) alcohols possessing one or more —CH₂OH groups therebyaffording hydrogen gas and the corresponding esters or lactons,according to the following scheme. In one embodiment this process is ahomogeneous dehydrogenation process, that can be used in place of theexisting heterogeneous techniques, preferably using base-free reactionconditions and avoiding high reaction temperatures.

Accordingly, one embodiment provides a process for dehydrogenation ofalcohols using metal catalysts based on the LNN′ ligand of Formula I.According to an embodiment of the invention, the substrates arecompounds of the following formulae:

In this embodiment, R groups, simultaneously or independently, representa linear, branched C₁-C₄₀ or cyclic C₃-C₄₀ alkyl, alkenyl or aromaticgroup, optionally substituted. Also, one may cite a situation when R isC₄-C₄₀ saturated or an unsaturated cyclic radical. This implies that thesubstrate can be any organic compound containing one, or more than one,hydroxyl (—OH) group. When the substrate is an alcohol or diol, theproducts are an ester or a lactone, respectively.

According to one embodiment, the process of catalytic acceptorlessdehydrogenation implies the usage of at least one of the metal complexesof Formulae II or III and (optionally) the use of a base and a solvent.The base may be necessary in those cases when the metal catalyst ofFormula II contains one or more halogen or alkoxy (—OR) groups bonded tothe metal. The catalyst can be treated with base prior to mixing withthe substrate or in situ by adding base to the reaction mixture duringdehydrogenation. The catalysts and pre-catalysts described herein can beused in a wide range of concentration, preferably between 10-1000 ppm,and the loadings of 1000 ppm or less are particularly preferred. Thepreferred amount of the catalyst will depend, as it is known to theperson skilled in the art, on the type of the substrate; and increasingthe catalyst loading should result in faster dehydrogenation. Thetemperature at which the dehydrogenation can be carried out is comprisedbetween 0° C. and 200° C., more preferably in the range between 50° C.and 150° C. and, as it is known to the person skilled in the art, thereaction rate will increase with increase of the reaction temperature.The dehydrogenation process can generate a pressure of H₂ gas and, insuch case, can be performed in a suitable pressure vessel, if necessaryequipped with a pressure-release valve.

It should be well understood, however, that the catalyst complexesdescribed herein are also useful in catalyzing dehydrogenation ofsubstrates including functional groups other than alcohols. The tablebelow provides a non-limiting list of substrates and correspondingproducts that can be formed from a catalytic dehydrogenation reactionusing a catalyst of Formula II or III.

Substrate Product^(a) alcohols ester alcohol aldehyde alcohol ketonediol lactone amine + alcohol amide amine + alcohol substituted amineamine + alcohol imine ammonia-borane aminoboranes ammonia-boraneborazine amine imine amines guanidine alcohol + thiol thioester thiolsulphoxide alcohol + phosphine acyl phosphine ^(a)H₂ is also a byproductof these reactions, it is either liberated from the reaction as H₂ ortransferred to an acceptor.

As noted above, a byproduct of the dehydrogenation reactions is H₂.Accordingly, the present application further provides a process forproducing H₂. The process can conveniently make use of readily availablesubstrates in a straightforward catalytic dehydrogenation process underrelatively mild conditions to generate H₂.

To gain a better understanding of the invention described herein, thefollowing examples are set forth. It should be understood that theseexamples are for illustrative purposes only. Therefore, they should notlimit the scope of this invention in any way.

EXAMPLES

Unless mentioned otherwise, all manipulations were performed under aninert gas (argon or nitrogen) in gloveboxes or using standard Schlenktechniques. NMR spectra were recorded on a Varian Unity Inova 300 MHzspectrometer. All ³¹P chemical shifts are relative to 85% H₃PO₄. ¹H and¹³C chemical shifts were measured relative to the solvent peaks but arereported relative to TMS. OsO₄ and RuCl₃.3H₂O were purchased fromPressure Chemicals. All other chemicals and anhydrous grade solventswere obtained from Aldrich and Alfa Aesar. Commercial anhydrous gradeethanol was further distilled over sodium metal and stored in the argonglovebox. (NEt₄)₂OsCl₆, RuHCl(CO)(AsPh₃)₃, OsHCl(CO)(AsPh₃)₃,RuCl₂(PPh₃)₃, RuCl₂(CO)(DMF)(PPh₃)₂ were prepared according topreviously reported methods. (Gusev, D. G., Dolgushin, F. M., Antipin,M. Yu. Organometallics 2001, 20, 1001; Spasyuk, D., Smith, S., Gusev, D.G. Angew. Chem. 2012, 51, 2772-2775; Shaw, A. P., Ryland, B. L., Norton,J. R., Buccella, D., Moscatelli, A. Inorg. Chem. 2007, 46, 5805-5812;Rajagopal, S., Vancheesan, S., Rajaram, J., Kuriacose, J. C. J. Mol.Cat. 1983, 22, 131-135, all incorporated herein by reference.)

Example 1—Synthesis of PyCH₂NH(CH₂)₂N(iPr)₂

2-aminoethyl diisopropylamine (6.32 g, 0.044 mmol) was added to2-picolyl aldehyde (4.70 g, 0.044 mmol) and the mixture was stirred for1 h. The obtained imine was diluted with methanol (15 mL) and NaBH₄(1.66 g, 0.044 mmol) was added portion-wise during 1 h. Then, allvolatiles were removed under vacuum, and the residue was re-dissolved in20 mL of dichloromethane. The solution was filtered through a short pad(3×2 cm) of Al₂O₃. The aluminum oxide was then washed with 10 mL ofdichloromethane and the collected filtrate was evaporated and driedunder vacuum for 1 h. The product was obtained as a yellow oil (8.41 g,90%).

¹H NMR (300 MHz, CDCl₃) δ=8.47 (ddd, J=4.8, 1.8, 0.9 Hz, 1H), 7.73 (td,J=7.6, 1.8 Hz, 1H), 7.39 (d, J=7.8 Hz, 1H), 7.21 (ddd, J=7.5, 4.9, 1.2Hz, 1H), 3.77 (s, 2H), 3.33 (br., 1H, NH), 2.97 (sep, J=7.0, 2H; CH),2.48 (m, J=2.5 Hz, 4H, CH₂), 0.92 (d, J=6.6 Hz, 12H; 4×CH₃).

¹³C NMR ([D6]DMSO) δ=160.62 (s, 1C; Py), 148.75 (s, 1C; Py), 136.33 (s,1C; Py), 121.75 (s, 1C; Py), 121.65 (s, 1C; Py), 54.71 (s, 1C; CH₂),49.23 (s, 1C; CH₂), 47.65 (s, 2C; CH), 44.14 (s, 1C; CH₂), 20.72 (s, 1C;4×CH₃).

Example 2—Synthesis of PyCH₂NH(CH₂)₂P(iPr)₂

2-picolyl aldehyde (1.66 g, 0.0155 mmol) in 10 mL of THF was added to a10 wt % solution of 2-(di-i-propylphosphino)ethylamine in THF (26.0 g,0.0162 mmol) and the mixture was stirred for 1 h. The obtained imine wasthen treated with diisobutyl aluminum hydride (22.7 mL, 1.5 M intoluene, 0.0341 mmol) during 1 h (Caution!!! Exothermic reaction!) andleft to stir for 1 h. After that time, the solution was quenched with 1mL of water (Caution!!! Exothermic reaction!) and the obtainedsuspension was filtered through a short pad (3×2 cm) of basic alumina.The solids were washed with THF (3 ? 10 mL) and the collected filtratewas evaporated and dried under vacuum for 3 h. The product was obtainedas a yellow oil (2.84 g, 73%).

³¹P {¹H} NMR ([D6]Benzene) δ=−1.0 (s). ¹H NMR ([D6]Benzene) δ=8.49 (dt,J=4.7, 1.8 Hz, 1H; Py), 7.15-7.13 (m, 1H; Py), 7.09 (td, J=7.7, J=1.8Hz, 1H; Py), 6.64 (ddd, J=7.0, 4.9, 1.7 Hz, 1H; Py), 3.93 (s, 2H;PyCH₂), 2.81 (m, 2H; NCH₂), 1.78 (br. s, 1H; NH), 1.65-1.35 (m, 4H; PCHand CH₂P), 1.01 (dd, J=13.8, 7.1 Hz, 6H; CH₃), 0.96 (dd, J=10.8, 7.0 Hz,6H; CH₃). ¹³C {¹H} NMR ([D6]Benzene) δ=161.37 (s, 1C; Py), 149.49 (s,1C; Py), 135.85 (s, 1C; Py), 121.92 (s, 1C; Py), 121.60 (s, 1C; Py),55.72 (s; 1C; NCH₂), 49.12 (d, J(CP)=24.9 Hz, 1C; NCH₂), 23.72 (d,J(CP)=13.5 Hz, 2C; PCH), 23.37 (d, J(CP)=19.3 Hz, 1C; PCH₂), 20.29 (d,J(CP)=16.5 Hz, 2C; CH₃), 18.93 (d. J(CP)=9.9 Hz, 2C; CH₃).

Example 3—Synthesis of trans-OsHCl(CO)[PyCH₂NH(CH₂)₂P(iPr)₂]

A flask containing a mixture of OsHCl(CO)AsPh₃)₃ (5.94 g, 5.57 mmol) andPyCH₂NH(CH₂)₂P(iPr)₂ (1.27 g, 5.06 mmol) in 15 mL of diglyme was placedin a preheated to 160° C. oil bath and stirred for 1 h, affording adark-red solution. After cooling to room temperature, the mixture wasdiluted with 4 mL of diethylether, and the flask was stored overnight ina freezer at 18° C. The precipitated product was filtered off, washedwith diethyl ether (3×3 mL), and dried under vacuum for 3 h to give abrown crystalline solid. Yield: 1.81 g (71%).

³¹P {¹H} NMR ([D2]DCM) δ=48.41 (s). ¹H {³¹P} NMR ([D2]DCM) δ=9.00 (d,J=5.5 Hz, 1H, Py), 7.68 (td, J=7.8, 1.5 Hz, 1H, Py), 7.28-7.16 (m, 1H,Py), 4.61 (dd, J=14.3, 4.4 Hz, 1H, PyCH₂), 4.12 (br. t, J=12.0 Hz, 1H,NH), 3.93 (dd, J=14.2, 11.6 Hz, 1H, PyCH₂), 3.67-3.58 (m, 1H, NCH₂),2.73-2.53 (m, 1H, NCH₂), 2.46 (sep, J=14.7, 7.4 Hz, 1H, PCH), 2.37 (dd,J=15.0, 4.0 Hz, 1H, CH₂P), 2.11 (sept, J=6.9 Hz, 1H, PCH), 1.77 (td,J=14.6, 5.8 Hz, 1H, CH₂P), 1.35 (d, J=7.4 Hz, 3H, CH₃), 1.21 (d, J=7.2Hz, 3H, CH₃), 1.09 (d, J=6.9 Hz, 3H, CH₃), 1.04 (d, J=7.0 Hz, 3H, CH₃),−16.45 (s, 1H, OsH, satellites J(OsH)=95.22). ¹³C {¹H} NMR ([D2]DCM)δ=188.57 (d, J(CP)=8.6 Hz, CO), 161.56 (s, 1C, Py), 153.89 (d, J(CP)=1.7Hz, 1C; Py), 136.16 (s, 1C; Py), 125.13 (d, J(CP)=2.0 Hz, 1C; Py),121.80 (d, J(CP)=1.7 Hz, 1C; Py), 60.62 (d, J(CP)=2.3 Hz, 1C; CH₂),54.96 (d, J(CP)=1.7 Hz, 1C; CH₂), 33.07 (d, J(CP)=25.9 Hz, 1C; CH),29.19 (d, J(CP)=30.3 Hz, 1C; CH), 26.03 (d, J(CP)=33.1 Hz, 1C; CH₂),21.04 (d, J(CP)=3.9 Hz, 1C; CH₃), 20.57 (d, J(CP)=3.4 Hz, 1C; CH₃),19.05 (s, 1C; CH₃), 17.51 (d, J(CP)=4.6 Hz, 1C; CH₃). IR (Nujol):ν_(C═O)=1879 (s) Anal. Calc'd for C₁₅H₂ClN₂OOsP: C, 35.53; H, 5.17; N,5.24. Found: C, 35.35; H, 5.19; N, 5.24.

Example 4—Synthesis of μ^(N)-mer,fac-{OsH(CO)[PyCH₂N(CH₂)₂P(iPr)₂]}₂

A mixture of OsHCl(CO)[PyCH₂NH(CH₂)₂P(iPr)₂] (1.00 g, 1.97 mmol) andKOtBu (243 mg, 2.17 mmol) in 7 mL of THF was stirred for 2 h, then theresulting solution was placed in a freezer for 1 h. The red reactionmixture was filtered into a 20 mL vial, and 1 mL of THF was used torinse the fritted funnel. The solution was diluted with 6 mL of diethylether and the compound was crystallized in a freezer at −18° C. Thecrystalline bright-yellow product was isolated by filtration and driedunder vacuum for 1 h. Yield: 621 mg (67%).

³¹P NMR ([D2]DCM) δ=67.73 (s), 51.50 (s). ¹H {³¹P} NMR ([D2]DCM) δ=8.86(t, J=6.7 Hz, 2H, Py), 7.08 (t, J=7.8 Hz, 1H, Py), 7.01 (t, J=7.6 Hz,1H, Py), 6.86-6.73 (m, 2H, Py), 6.34 (d, J=8.0 Hz, 1H, Py), 6.24 (d,J=7.8 Hz, 1H, Py), 5.24 (d, J=17.8 Hz, 1H, PyCH₂), 4.72 (d, J=19.4 z,1H, PyCH₂), 4.14 (d, J=17.7 Hz, 1H, NCH₂), 3.84 (t, =12.9 Hz, 1H, NCH₂),3.80-3.68 (m, 1H), 3.56-3.33 (m, 3H), 2.75 (hept, J=14.4, 1H; CH),2.39-2.17 (m, 2H), 2.05 (hept, J=5.6, 1H, PCH), 1.99-1.87 (m, 1H),1.83-1.62 (m, 1H), 1.32 (2d overlapped, J=−7.4 Hz, 3H), 1.28-1.16 (m,1H), 1.09 (d, J=6.9 Hz, 3H; CH₃), 1.05 (d, J=6.8 Hz, 3H; CH₃), 0.95 (d,J=6.7 Hz, 3H; CH₃), 0.89 (d, J=6.9 Hz, 3H; CH₃), 0.73 (d, J=7.0 Hz, 3H;CH₃), 0.58 (t, J=7.3 Hz, 3H), −11.54 (s, 1H; OsH), −14.31 (s, 1H; OsH).¹³C {¹H} NMR ([D2]DCM) δ=191.26 (d, J(CP)=9.0 Hz, 1C; CO), 190.06 (d,J(CP)=6.7 Hz, 1C; CO), 171.19 (s, 1C; Py), 170.65 (s, 1C; Py), 151.05(s, 1C; Py), 150.77 (s, 1C; Py), 133.61 (s, 1C; Py), 133.36 (s, 1C; Py),122.96 (d. J(CP)=2.0 Hz, 1C; Py), 122.80 (s, 1C; Py), 117.82 (s, 1C;Py), 75.84 (s, 1C; PyCH₂), 74.06 (s, 1C; PyCH₂), 70.28 (d, J(CP)=6.5 Hz,1C; NCH₂), 68.89 (s, 1C; NCH₂), 36.42 (d, J(CP)=28.7 Hz, 1C; CH), 30.73(d, J(CP)=21.3 Hz, 1C; CH), 29.15 (d, J(CP)=36.4 Hz, 1C; CH), 28.59 (d,J(CP)=21.8 Hz, 1C; CH), 26.46 (d, J(CP)=22.2 Hz, 1C; CH₂), 26.01 (d,J(CP)=32.2 Hz, 1C; CH₂), 22.32 (d, J(CP)=3.6 Hz, 1C; CH₃), 20.91 (d,J(CP)=4.7 Hz, 1C; CH₃), 20.17 (d, J(CP)=2.3 Hz, 1C; CH₃), 19.77 (s, 1C;CH₃), 19.58 (d, J(CP)=2.3 Hz, 1C; CH₃), 19.09 (s, 1C; CH₃), 18.26 (s,1C; CH₃), 16.77 (d, J(CP)=7.0 Hz, 1C; CH₃).

Example 5—Synthesis of RuHCl(CO)(AsPh₃)₃

A 250 mL round-bottom Schlenk flask was loaded in air with RuCl₃.3H₂O(1.26 g, 4.85 mmol), AsPh₃ (5.94 g, 19.4 mmol), NEt(iPr)₂ (5.00 g, 38.7mmol), 2-methoxyethanol (115 mL) and aqueous formaldehyde (40%, 15 mL).The stoppered flask was briefly opened to vacuum and refilled withargon; this procedure was repeated five times. The stirred reactionmixture was heated in an oil bath for 4 h while maintaining the bathtemperature at 125° C. The resulting greyish suspension was left at roomtemperature for 1 h. The precipitate was filtered off, washed withethanol (3×5 mL), and dried under vacuum for 2 h to give an off-whitesolid. Yield: 3.14 g (66%).

Example 6—Synthesis of trans-RuHCl(CO)[PyCH₂NH(CH₂)₂P(iPr)₂]

A 25 mL Schlenk flask containing a mixture of RuHCl(CO)(AsPh₃)₃ (2.13 g,2.18 mmol) and PyCH₂NH(CH₂)₂P(iPr)₂ (500 mg, 1.98 mmol) in 20 mL oftoluene was stirred under reflux for 1 h at 110° C. affording a darkbrown solution. After cooling to room temperature, the product wasfiltered giving a pale brown powdery solid that was washed withdiethylether (2×5 mL) and dried under vacuum. Yield: 671 mg (81%).

³¹P {¹H} NMR ([D2]DCM) δ=94.74 (s). ¹H {³¹P} NMR ([D2]DCM) δ=8.93 (d,J=5.3 Hz, 1H; Py), 7.68 (td, 0.1=7.7, 1.6 Hz, 1H; Py), 7.32-7.12 (m, 2H;Py), 4.41 (d, 0.1-10.2 Hz, 1H; CH₂), 4.20-3.95 (m, 2H; NH+CH₂),3.57-3.40 (m, 1H; CH₂), 2.62 (ddd, J=11.3, 9.3, 3.9 Hz, 1H; CH₂), 2.50(sep, J=−7.1 Hz, 1H; CH), 2.30 (dd, J=15.0, 3.8 Hz, 1H; CH₂), 2.19 (sep,J=6.9 Hz, 1H; CH), 1.91 (td, J=14.6, 5.9 Hz, 1H; CH₂), 1.38 (d, J=7.4Hz, 3H; CH₃), 1.21 (d, J=7.2 Hz, 3H; CH₃), 1.15-1.01 (overlapped d, 6H;2CH₃), −14.93 (s, 1H; RuH). ¹³C {¹H} NMR ([D2]DCM) δ=206.52 (dd due tocoupling to ³¹P and the residual coupling to the hydride, J(CP)=15.3,7.3 Hz, 1C; CO), 160.91 (s, 1C; Py), 153.65 (d, J(CP)=1.3 Hz, 1C; Py),136.79 (s, 1C; Py), 124.42 (d, J(CP)=2.0 Hz, 1C; Py), 121.57 (d,J(CP)=1.5 Hz, 1C; Py), 59.80 (s, 1C; PyCH₂), 52.98 (s, 1C; NCH₂), 32.58(d, J(CP)=21.3 Hz, 1C; PCH₂), 29.02 (d, J(CP)=24.9 Hz, 1C; CH), 25.03(d, J(CP)=28.5 Hz, 2C; CH), 20.69 (d, J(CP)=4.2 Hz, 2C; 2×CH₃), 19.05(s, 1C; CH₃), 17.61 (d, J(CP)=5.2 Hz, 1C; CH₃).

Example 7—Hydrogenation of Esters Using Complexes 1

tBuOK (15 mg, 0.13 mmol) was added to a solution of complex 1 (51 mg,0.10 mmol) in 10 mL of THF and the mixture was stirred for 3 min. 1 mLof the obtained solution was mixed with methyl benzoate (2.72 g, 20.0mol) or other desired substrate in 6 mL of THF or toluene. The mixturewas then placed into a 75 mL stainless-steel reactor (Parr 4740)equipped with a magnetic stir bar. The reactor was purged by two cyclesof pressurization/venting with H₂ (150 psi, 10 Bar) and then pressurizedwith H₂ (725 psi, 50 Bar) and disconnected from the H₂ source. Thereaction was conducted for 1.5 h at 100° C. in a preheated oil bath. Atthe end of the reaction time, the reactor was placed into a cold waterbath and it was depressurized after cooling to the ambient temperature.The product benzyl alcohol was obtained after evaporation of allvolatiles (THF, CH₃OH) under vacuum. The results are shown in tables 1-4below. See table 2 for a complete list of tested substrates.

TABLE 1 Hydrogenation of methyl benzoate catalyzed by complexes 1-3, 7and 9^([a])

Entry Catalyst Ester/[M]^([b]) T, ° C. Time, h Conv., %  1 1^([c])  2000100 1.5 100  2 2  2000 40 22 28  3 2  2000 60 7 82  4 2  2000 80 2.2 76 5 2  2000 100 1.5 99  6 2  3000 100 3 100  7 2 10000^([d]) 100 19 80  83^([c])  2000 100 1.7 100  9 9  2000 40 17 82 10 9  2000 60 2.2 71 11 9 2000 80 1.2 88 12 9  2000 100 1 99 13 9 10000 100 14 100 14 9 20000 10017 90 15 7  4000 40 16 98 ^([a])20 mmol of PhCOOMe in 7 mL of THF washydrogenated in a 75 mL Parr pressure vessel. ^([b])Substrate to metalmolar ratio. ^([c])With 1 mol % of tBuOK. ^([d])120 mmol of PhCOOME, ina 300 mL vessel.

TABLE 2 Hydrogenation of esters (A-J) and imines (K, L) that affordedthe corresponding alcohols and amines, catalyzed by complexes 2, 7 and9^([a]). A

B

C

D

E

F

G

H

I

J

K

L

Entry Ester Catalyst Ester/[M]^([b]) Temp., ° C. Time, h Conv., %  1 A 22000 100 1.6 99  2 B 2 2000 100 1.5 93  3 C 2 2000 100 17 0  4 D 2 2000100 2 100  5 D 2^([c]) 3000 100 2.7 100  6 D 9 2000 100 1.5 93  7 D 910000 100 18 71  8 D 7^([d]) 20000 40 18 94  9 E 2 2000 100 3 100 10 E7^([e]) 20000 40 16 100 11 F 2 2000 100 1.4 99 12 F 9 2000 100 5 67 13 G2 2000 100 9 72 14 G 7^([f]) 2000 40 16 98 15 H 2 2000 100 21 0 16 I 92000 100 5.7 85 17 J 7^([g]) 4000 40 16 100 18 K 7^([g]) 50000 40 16 10019 L 7^([g]) 2000 40 16 100 ^([a])20 mmol of substrate in 7 mL of THFwas hydrogenated in a 75 mL pressure vessel under p(H₂) = 50 Bar.[b]Substrate to metal molar ratio. ^([c])120 mmol of substrate, using a300 mL vessel. ^([d])With 5 mol % of KOMe. ^([e])With 1 mol % of NaOEt.^([f])With 10 mol % of KOMe. ^([g])With 1 mol % of tBuOK.

TABLE 3 Exemplary Substrate-Product pairs Substrate Product

TABLE 4 Hydrogenation of fatty esters catalyzed by complexes 2, 3 and9^([a]) Substrate

Product Conversion

100%

100%

100%      0%

 99%

 8%    32%    60%

98%

ca. 90% ^([a])with tBuOK., 0.5 mol %. ^([b])A mixture of triglyceridesof oleic (ca. 5%), linoleic (ca. 2-3%), and palmitic acids as the maincomponents in our samples.

Example 8—Hydrogenation of Methyl Benzoate Using Complex 2

1 mL of a solution containing 4.7 mg/mL of 2 (0.01 mmol [Os]) in THF ortoluene was added to a solution of methyl benzoate (2.72 g, 20.0 mmol)in 6 mL of THF or toluene. The subsequent manipulations were carried outfollowing the procedure in Example 7.

Example 9—Hydrogenation of Olive Oil Using Complex 2

0.6 mL of a 4.7 mg/mL solution of 2 in toluene (containing 0.006 mmol[Os]) was added to a solution of olive oil (1.86 g, 2.00 mmol) in 6 mLof toluene. All subsequent manipulations were carried out following theprocedure in Example 7 using a 7 h reaction time. The product mixturewas evaporated and dried under vacuum for 1 h. Further separation of thefatty alcohol from glycerol could be performed by hexane extraction orby centrifugation and decantation of the fatty alcohol from glycerol.

Example 10—Hydrogenation of Methyl Caproate Using Complex 3

1 mL of a 4.2 mg/mL solution of 3 (0.01 mmol) in THF or toluene andtBuOK (22.6 mg, 0.2 mmol) were added to a solution of methyl caproate(2.94 g, 20.0 mmol) in 6 mL of THF or toluene. All subsequentmanipulations were carried out following the procedure described inExample 7.

Example 11—Synthesis of NH₂(CH₂)₂PPH₂

In a 500 mL flask, 50.0 g (0.191 mol) of PPh₃ was dissolved in 200 mL ofTHF and 4.00 g (0.571 mol) of granulated Li was added. The mixturerapidly changed color to bright-orange, then to dark-red. The reactionwas stirred overnight, and then the product solution was filteredthrough a glass frit into a 500 mL flask. Slow addition of 19.3 g (0.166mol) of 2-chloroethylamine hydrochloride to the filtrate (Caution:Exothermic reaction!) afforded a light-orange solution that was left tostir for an additional 30 min and then was treated with 3.00 g of H₂O.Solvent removal under vacuum afforded a viscous residue. The crudeproduct was washed with 3×20 mL of hexane and the remaining white slurrywas extracted with 70 mL of toluene and filtered through a short plug (2cm×1 cm) of Al₂O₃. The toluene extract was evaporated using a rotavapand subsequently dried under vacuum to give 34.69 g (91%) of crude(83-85%) NH₂(CH₂)₂PPh₂ as a light-yellow oil. This product was usedwithout purification in the synthesis of Example 12.

Example 12—Synthesis of PyCH═NCH₂CH₂PPh₂

A solution of 2-picolyl aldehyde (23.2 g, 0.216 mol) in 20 mL of THF wasslowly added to 60 g (83%, 0.218 mol) of 2-aminoethyl diphenylphosphinein 80 mL of THF and the mixture was stirred for 3 h. Then, 40 mL ofhexane was added and the mixture was left in a refrigerator at −18° C.,which produced an off-white precipitate. The solid was filtered off,washed with denatured ethanol (2×10 mL) and 40 mL of hexane, and thendried under vacuum for 2 h. The product was obtained as an off-whitesolid. Yield 47.2 g (68%).

¹H NMR ([D6]Benzene) δ=8.54-8.33 (m, 2H, Py+NCH), 8.09 (dd, J=7.9, 1.0Hz, 1H, Py), 7.54-7.32 (m, 4H, Ph), 7.12-6.99 (m, 7H, Ph+Py), 6.71-6.53(m, 1H, Py), 3.79-3.55 (m, 2H, CH₂), 2.46-2.24 (m, 2H, CH₂). ¹³C NMR([D6]Benzene) δ=162.70 (s, 1C, Py), 155.78 (s, 1C, N═C), 149.64 (s, 1C,Py), 139.56 (d, J(CP)=14.3 Hz, 2C, {ArP}C^(ipso)), 136.05 (s, 1C, Py),133.30 (d, J(CP)=19.0 Hz, 4C, {ArP}C^(ortho)), 128.87 (s, 2C,{Ar}C^(para)), 128.78 (s, 4C, {Ar}C^(meta)), 124.53 (s, 1C, Py), 121.04(s, 1C, Py), 58.45 (d, J(CP)=20.3 Hz, 1C, NCH₂), 30.50 (d, J(CP)=13.9Hz, 1C, CH₂P). ³¹P NMR ([D6]Benzene) δ=−18.19 (s).

Example 13—Synthesis of PyCH₂NH(CH₂)₂PPh₂

40 g (0.126 mol) of PyCH═NCH₂CH₂PPh₂ was suspended in 100 mL of methanolin a 250 mL flask, followed by slow addition of 5.24 g (0.138 mol) ofNaBH₄ over a 2 h period of time. After further stirring for 30 min, themixture was evaporated and the oily residue was extracted with 3×30 mLof toluene. The toluene solution was filtered through a short plug ofAl₂O₃ (2 cm×2 cm), using additional 2×20 mL of toluene to wash thesolids. The solvent was removed under vacuum and the product was driedfor an additional 2 h to yield 37.2 g (92%) of a pale-yellow oil thatcrystallized upon further standing (after 7-10 days) at roomtemperature.

¹H NMR ([D6]Benzene) δ=8.46 (ddd, J=4.8, 1.7, 1.0 Hz, 1H, Py), 7.53-7.31(m, 4H, Ph), 7.12-6.91 (m, 6H, Ph), 6.62 (ddd, J=7.2, 4.8, 1.5 Hz, 1H,Py), 3.79 (s, 2H, CH₂), 2.75 (dd, J=15.2, 8.5 Hz, 2H, CH₂), 2.25-2.02(m, 2H, CH₂), 1.67 (br. s, 1H, NH). ¹³C {¹H} NMR ([D6]Benzene) δ=161.06(s, 1C, Py), 149.48 (s, 1C, Py), 139.74 (d, J(CP)=14.2 Hz, 2C,{ArP}C^(ipso)), 135.84 (s, 1C, Py), 133.18 (d, J(CP)=18.8 Hz, 4C,{ArP}C^(ortho)), 128.69 (d, J(CP)=6.5 Hz, 4C, {ArP}C^(meta)), 128.62 (s,2C, {ArP}C^(para)), 121.94 (s, 1C, Py), 121.61 (s, 1C, Py), 55.39 (s,1C, CH₂N), 46.79 (d, J(CP)=20.7 Hz, 1C, NCH₂), 29.79 (d, J(CP)=12.9 Hz,1C, CH₂P).

Example 14—Synthesis of trans-OsHCl(CO)[PyCH₂NH(CH₂)₂PPh₂]

A flask containing a mixture of OsHCl(CO)(AsPh₃)₃ (3.00 g, 2.56 mmol)and PyCH₂NH(CH₂)₂PPh₂ (0.818 g, 2.56 mmol) in 30 mL of diglyme wasplaced in an oil bath preheated to 160° C., and stirred for 3 haffording a dark-red solution. After cooling to room temperature, themixture was diluted with 30 mL of hexane, and the flask was stored for 1h in a freezer at −23° C. The precipitated product was filtered off,washed with diethyl ether (3×5 mL), and recrystallized from 20 mLDCM:Et₂O mixture (3:1). Yield: 779 mg (53%).

¹H {³¹P} NMR ([D2]DCM) δ=9.04 (d, J=5.1 Hz, 1H, Py), 7.81-7.59 (m, 5H,Ph+Py), 7.45-7.30 (m, 6H, Ph), 7.28-7.16 (m, 2H, Py), 4.64 (dd, J=14.6,4.4 Hz, 1H, CH₂), 4.50 (br t, J=−11.5 Hz, 1H, NH), 3.96 (dd, J=14.1,11.7 Hz, 1H, CH₂), 3.80-3.67 (m, 1H, CH₂), 3.09 (dd, J=14.5, 1.9 Hz, 1H,CH₂), 2.74 (dtd, J=14.7, 11.6, 3.3 Hz, 1H, CH₂), 2.32 (td, J=14.6, 5.4Hz, 1H. CH₂), −15.81 (s, 1H, OsH). ¹³C {¹H} NMR ([D2]DCM) δ=188.19 (dd,J(CP)=9.2, 5.6 Hz, residual coupling with OsH, 1C, CO), 161.63 (s, 1C,Py), 154.20 (d, J(CP)=1.5 Hz, 1C, Py), 139.78 (d, J(CP)=54.6 Hz, 1C,{Ar}C^(ipso)), 136.70 (s, 1C, Py), 135.90 (d, J(CP)=50.4 Hz, 1C,{Ar}C^(ipso)), 133.61 (d, J(CP)=10.9 Hz, 1C, 2C, {Ar}C^(ortho)), 132.69(d, J(CP)=10.8 Hz, 2C, {Ar}C^(ortho)), 130.50 (d, J(CP) 2.4 Hz, 1C,{Ar}C^(para)), 130.36 (d, J(CP)=2.4 Hz, 2C, {Ar}C^(para)), 128.82 (d,J(CP)=10.4 Hz, 2C, {Ar}C^(meta)), 128.66 (d, J(CP)=10.4 Hz,{Ar}C^(meta)), 125.34 (d, J(CP)=2.0 Hz, Py), 122.02 (d, J(CP)=1.5 Hz,Py), 60.63 (s, 1C, PyCH₂), 53.73 (d, J(CP)=2.1 Hz, 1C, NCH₂), 35.91 (d,J(CP)=30.8 Hz, 1C, CH₂P). ³¹P {¹H} NMR ([D2]DCM) δ=29.7 (s).

Example 15—Synthesis of trans-RuHCl(CO)[PyCH₂NH(CH₂)₂PPh₂]

A 50 mL Schlenk flask containing a mixture of RuHCl(CO)(AsPh₃)₃ (5.73 g,4.68 mmol) and PyCH₂NH(CH₂)₂PPh₂ (1.5 g, 4.68 mmol) in 30 mL of dioxanewas stirred under reflux for 3 h affording a dark brown solution. Aftercooling to room temperature, the mixture was diluted with 5 mL of Et₂Oand left in a refrigerator at −15° C. The crystallized product wasfiltered, then washed with diethyl ether (2×5 mL), and dried undervacuum. Yield: 1.71 g (75%) of a grey solid.

¹H {³¹P} NMR ([D2]DCM) δ=8.97 (d, J=5.4 Hz, 1H, Py), 7.95-7.55 (m, 5H,Ph+Py), 7.47-7.35 (m, 6H, Ph), 7.33-7.26 (m, 1H, Py), 7.22 (d, J=7.8 Hz,1H, Py), 4.45 (dd, J=15.3, 4.2 Hz, 2H, PyCH₂), 4.09 (dd, J=15.3, 12.7Hz, 1H, CH₂), 3.71-3.51 (br, 1H, NH), 3.00 (dd, J=14.1, 1.8 Hz, 1H,CH₂), 2.75 (dtd, J=−14.3, 11.3, 3.1 Hz, 1H, CH₂), 2.53 (td, J=14.4, 5.1Hz, 1H, CH₂), −14.30 (s, 1H, RuH). ¹³C {¹H} NMR ([D2]DCM) δ=205.80 (d,J(CP)=17.9 Hz), 160.84 (s, 1C, Py), 153.92 (d, J(CP)=1.1 Hz, 1C, Py),138.73 (d, J(CP)=49.5 Hz, 1C, {Ar}C^(ipso)), 137.14 (s, 1C, Py), 135.66(d, J(CP)=43.7 Hz, 1C, {Ar}C^(ipso)), 133.46 (d, J(CP)=11.0 Hz, 2C,{Ar}C^(ortho)), 132.62 (d, J(CP)=11.4 Hz, 2C, {Ar}C^(ortho)), 130.44 (d,J(CP)=2.4 Hz, 1C, {Ar}C^(para)), 130.34 (d, J(CP)=2.3 Hz, 1C,{Ar}C^(para)), 128.84 (d, J(CP)=10.1 Hz, 2C, {Ar}C^(meta)), 128.61 (d,J(CP)=10.1 Hz, 2C, {Ar}C^(meta)), 124.61 (d, J(CP)=2.2 Hz, 1C, Py),121.75 (d, J(CP)=1.6 Hz, 1C, Py), 59.77 (d, J(CP)=1.5 Hz, 1C, CH₂),51.92 (d, J(CP)=4.1 Hz, 1C, CH₂), 35.14 (d, J/(CP)=26.0 Hz, 1C, CH₂).Anal. Calcd for C₂₀H₂₁ClN₂ORuP: C, 47.23; H, 6.61; N, 7.34. Found: C,46.95; H, 6.53; N, 7.15.

Example 16—Typical Procedure for Acceptorless Alcohol Dehydrogenation

A 50 mL Schlenk flask equipped with a stir bar was charged with 0.052mmol of Complex 2, 3, or 5, 0.5-1 mol % of tBuOK (with 3 and 5), and thecalculated amount of substrate (1000:1, substrate to metal ratio) underargon. Then, the flask (attached to and vented through an argonmanifold) was placed in an oil bath, where it was heated at atemperature slightly exceeding the boiling point of the neat alcohol.The conversion was monitored by 1H NMR spectroscopy using 0.6 mL samplesretrieved from the reaction solutions through the septum stopper withthe help of a syringe.

TABLE 5 Results of catalytic acceptorless dehydrogenation of alcohols.Conversion, Entry R^([a]) T, ° C. cat ROH/[M]^([b]) t, h % 1 Me 785^([e]) 1000 7.5 9 2 Me 78 5^([c, e]) 1000 19 25 3 Me 78 2 1000 24 7 4Me 78 2^([e]) 1000 8 61 5 Me 78 2^([c, d]) 1000 8 96 6 Me 78 3^([d])1000 7.5 30 7 Me 78 7^([f]) 2000 16 95 8 Me 78 7^([g]) 10000 24 91 9 Me78 7^([g]) 20000 40 85 10 Me 78 7^([f][h]) 2000 16 89 11 Et 96 5^([e])1000 6 69 12 Et 96 2 1000 8.5 86 13 Et 96 3^([d]) 1000 8 73 14 Pr 1185^([e]) 1000 2 73 15 Pr 118 2 1000 3 93 16 Pr 118 3^([d]) 1000 3 78 17i-Amyl 131 5^([e]) 1000 2.5 88 18 i-Amyl 131 2 1000 3 86 19 i-Amyl 1313^([d]) 1000 2.5 92 20 Hexyl 158 5^([e]) 1000 2 86 21 Hexyl 158 2 10001.3 97 22 Hexyl 158 2 4000 1.3 71 23 Hexyl 158 3^([d]) 1000 1 86^([a])Using 52 mmol of neat substrate and 1 mol % of EtONa for catalyst7. ^([b])Substrate to metal molar ratio. ^([c])In toluene. ^([d])With0.5 mol % of tBuOK. ^([e])With 1 mol % of iBuOK. ^([f])Using 0.1 mol ofneat substrate. ^([g])Using 0.2 mol of neat substrate. ^([h])Reactionwas prepared in air using standard anhydrous grade ethanol

Example 17—Synthesis of PyCH₂NH(CH₂)₂PtBu₂

The synthesis of NH₂(CH₂)₂PtBu₂ was performed following a knownprocedure (6, incorporated herein by reference). A solution of 2-picolylaldehyde (2.04 g, 19.04 mmol) in 10 mL of THF was added to2-(di-tert-butylphosphino)ethylamine (3.60 g, 19.04 mmol) in 10 mL ofTHF. The mixture was stirred for 1 h, then evaporated and dried for 1 hunder vacuum. The oily residue was re-dissolved in 15 mL of toluene andwas slowly (over a period of 1 h) treated with 1.5M solution of DIBAL intoluene (16.5 mL, 24.75 mmol) (Caution: exothermic reaction!). Theproduct solution was stirred for 30 min, and then quenched with 1 mL ofwater (Caution: exothermic reaction!). The resulting suspension wasfiltered through a short plug (2.1 cm) of basic alumina and the solidswere washed with THF (3×10 mL). The filtrate was evaporated and driedunder vacuum for 3 h to give the product as a yellow oil (3.79 g, 71%).

¹H {³¹P} NMR ([D6]Benzene) δ=8.49 (d, J=4.8 Hz, 1H, Py), 7.19-7.15 (m,1H, Py overlapped with C₆D₅H) 7.10 (t, J=7.1 Hz, 1H, Py), 6.64 (dd,J=6.3, 5.8 Hz, 1H, Py), 3.96 (s, 2H, PyCH₂), 2.87 (t, J=7.7 Hz, 2H,NCH₂), 1.91 (br, 1H, NH) 1.56 (t, J=7.7 Hz, 2H, CH₂P), 1.07 (s, 18H,CH₃). ¹³C {¹H} NMR ([D6]Benzene) δ=161.46 (s, 1C, Py), 149.48 (s, 1C,Py), 135.84 (s, 1C, Py), 121.91 (s, 1C, Py), 121.58 (s, 1C, Py), 55.79(s, 1C, CH₂), 50.78 (d, J(CP)=34.2 Hz, 1C, CH₂), 31.19 (d, J(CP)=22.1Hz, 2C, CMe₃), 29.82 (d, J(CP)=14.0 Hz, 6C, CH₃), 22.96 (d, J(CP)=27.5Hz, 1C, CH₂P). ³¹P {¹H} NMR ([D6]Benzene) δ=20.47 (s).

Example 18—Synthesis of trans-RuHCl(CO)[PyCH₂NH(CH₂)₂PtBu₂]

A mixture of RuHCl(CO)(AsPh₃)₃ (1.93 g, 1.79 mmol) andPyCH₂NH(CH₂)₂PtBu₂ (500 mg, 1.79 mmol) in 10 mL of diglyme was stirredfor 3 h at 140° C. in a 50 mL Schlenk flask. After cooling to roomtemperature, 2 mL of Et₂O was added, and the mixture was left tocrystallize at −18° C. The product was filtered, washed with diethylether (2×3 mL), and dried under vacuum to give a grey solid. Yield: 431mg (54%).

¹H {³¹P} NMR ([D2]DCM) δ=8.89 (dt, J=5.4, 0.8 Hz, 1H; Py), 7.66 (td,J=7.7, 1.6 Hz, 1H; Py), 7.22 (dd, J=15.5, 7.2 Hz, 2H; Py), 4.68 (br.,1H; NH), 4.45 (dd, J=15.0, 4.7 Hz, 1H; CH₂), 4.00 (dd, J=14.9, 11.5 Hz,1H; CH₂), 3.61-3.44 (m, 1H; CH₂), 2.67 (dtd, J=13.4, 11.6, 4.8 Hz, 1H;CH₂), 2.26 (dd, J=14.7, 4.2 Hz, 1H; CH₂), 2.07 (td, J=14.2, 6.4 Hz, 1H;CH₂), 1.35 (d, J=5.3 Hz, 18H; CH₃), −15.59 (s, 1H; RuH), ¹³C {¹H} NMR([D2]DCM) δ 206.49 (dd, J(CP)=15.5, J(CH)=6.9 Hz residual coupling withOsH, 1C; CO), 160.73 (s, 1C; Py), 153.59 (s, 1C; Py), 136.74 (s, 1C;Py), 124.37 (d, J(CP)=1.6 Hz, 1C; Py), 121.33 (s, 1C; Py), 52.51 (s, 1C;CH₂), 38.29 (d, J(CP)=15.0 Hz, 1C; CH₂), 37.55 (d, J(CP)=24.6 Hz, 1C;CMe₃), 37.52 (d, J(CP)=24.6 Hz, 1C; CMe₃), 30.93 (d, J(CP)=4.3 Hz, 3C;CH₃), 30.07 (d, J(CP)=3.2 Hz, 3C; CH₃), 28.49 (d, J(CP)=14.9 Hz, 1C;PCH₂). ³¹P {¹H} NMR ([D2]DCM) δ 106.10 (s). Anal. Calcd forC₁₇H₃₁ClN₂OPRu: C, 45.68; H, 6.99; N, 6.27. Found: C, 45.40; H, 6.74; N,5.92.

Example 19—Synthesis of trans-RuCl₂(PPh)[PyCH₂NH(CH₂)₂PPh₂]

Stirring a mixture of RuCl₂(PPh)₃ (4.20 g, 4.38 mmol) andPyCH₂NH(CH₂)₂PPh₂ (1.40 g, 4.38 mmol) in 30 mL of toluene (or1,4-dioxane) for 3 h at 40° C. in a 100 mL Schlenk flask produced ayellow suspension. The product was filtered in air, washed with 10 mL ofEt₂O, and dried under vacuum for 2 h to give a yellow solid. Yield: 3.1g (94%).

¹H {³¹P} NMR ([D2]DCM) δ 8.42 (d, J=5.6 Hz, 1H; Py), 7.77-7.53 (m, 3H),7.53-6.91 (m, 29H), 6.85 (t, J=6.6 Hz, 1H; Py), 5.49 (t, J=13.0 Hz, 1H;CH₂), 5.23 (br, 1H; NH), 4.28 (dd, J=13.9, 3.5 Hz, 1H; CH₂), 3.66-3.31(m, 2H; CH₂), 2.91-2.57 (m, 2H; CH₂), 2.35 (s, 3H; CH₃Tol), ¹³C {¹H} NMR([D2]DCM) δ 163.50 (s, 1C; Py), 156.81 (s, 1C; Py), 139.44 (d, J=32.2Hz, 2C; {PPh₂}C^(ipso)), 137.89 (s, 1C; Py), 137.13 (d, J(CP)=39.3, 3C;{PPh₃}C^(ipso)), 135.95-135.29 (m, 6C; {PPh₃}C^(ortho)), 135.11 (d,J(CP)=8.4 Hz, 2C; {PPh₂}C^(ortho)), 134.47 (d, J(CP)=9.1 Hz, 2C;{PPh₂}C^(ortho)), 129.38 (d, J(CP)=4.5 Hz, 2C; {PPh₂}C^(para)), 129.38(s, 3C; {PPh₃}C^(para)), 128.48-127.05 (m, 10C;{PPh₂}C^(meta)+{PPh₃}C^(meta)), 122.96 (s, 1C; Py), 121.92 (s, 1C; Py),67.59 (s, 1,4-dioxane), 57.77 (s, 1C; CH₂), 49.09 (s, 1C; CH₂), 38.77(d, J(CP)=27.4 Hz, 1C; CH₂). ³¹P {¹H} NMR ([D2]DCM) δ 49.13 (d,J(PP)=28.9 Hz, 1P), 47.39 (d, J(PP)=29.0 Hz, 1P). Anal. Calcd forC₃₈H₃₆Cl₂N₂P₂Ru.C₇H₈: C, 63.83; H, 5.24; N, 3.31. Found: C, 63.23; H,5.22; N, 3.34.

Example 20—Synthesis of trans-OsHCl(CO)[PyCH₂NH(CH₂)₂PtBu₂]

A mixture of OsHCl(CO)AsPh₃)₃ (1.675 g, 1.43 mmol) andPyCH₂NH(CH₂)₂PtBu₂ (400 mg, 1.43 mmol) in 10 mL of diglyme was stirredfor 3 h at 140° C. in a 50 mL Schlenk flask. After cooling to roomtemperature, 2 mL of Et₂O was added, and the product crystallized uponstanding at −15° C. The yellow solid was filtered, washed with diethylether (2×3 mL) and dried under vacuum. Yield: 507 mg (66%).

¹H {³¹P} NMR ([D2]DCM) δ 8.97 (dt, J=6.3, 1.4 Hz, 1H; Py), 7.67 (td,J=7.8, 1.5 Hz, 1H; Py), 7.27-7.05 (m, 2H; Py), 4.65 (dd overlapping withbr. s, J=15.8, 4.7 Hz, 2H; CH₂+NH), 3.88 (dd, J=15.8, 12.2 Hz, 1H; CH₂),3.69-3.43 (m, 1H; CH₂), 2.64 (ddd, J=25.1, 11.4, 4.6 Hz, 1H; CH₂), 2.33(dt, J=29.2, 14.5 Hz, 1H; CH₂), 1.99 (td, J=14.4, 6.4 Hz, 1H; CH₂), 1.35(s, 18H; CH₃), −17.35 (s, 1H; OsH), ¹³C {¹H} NMR ([D2]DCM) δ 188.49 (dd,J(CP)=8.3, J(CH)=4.3 Hz residual coupling with OsH, 1C; CO), 161.44 (s,1C; Py), 153.79 (d, J(CP)=1.7 Hz, 1C; Py), 136.22 (s, 1C; Py), 125.08(d, J(CP)=1.8 Hz, 1C; Py), 121.55 (d, J(CP)=1.6 Hz, 1C; Py), 54.22 (s,1C; CH₂), 39.63 (d, J(CP)=20.8 Hz, 1C; CH₂), 38.96 (d, J(CP)=29.1 Hz,2C; CMe), 30.90 (d, J(CP)=3.9 Hz, 3C; CH₃), 29.78 (d, J(CP)=2.6 Hz, 3C;CH₃), 29.22 (d, J(CP)=19.8 Hz, 1C; CH₂). ³¹P {¹H} NMR ([D2]DCM) δ 62.79(s). Anal. Calcd for C₁₇H₃₁ClN₂OPOs: C, 38.16; H, 5.65; N, 5.24. Found:C, 38.04; H, 5.72; N, 4.97.

Example 21—Imine and Ester Hydrogenation Using Complex 7

Complex 7 was further tested in hydrogenation of compounds with polarC═X bonds. There has been much recent interest in the catalytichydrogenation of esters. Although the performance of the “state of theart” industrial catalysts is impressive, further improvements are highlydesirable to (a) reduce the reaction temperature, preferably to as lowas 20-40° C., and (b) reduce the catalyst loading, preferably to lessthan 0.05 mol %. Guided by these considerations, complex 7 was tested inthe hydrogenation of several benchmark substrates, shown in tables 1-4,above. Note that all of the reactions shown were performed at 40° C.

In an argon glovebox, the required amount of a 1.9 mg/g solution of 4 inTHF was added to the desired amount of base (tBuOK, MeOK, or EtOK). Theobtained mixture was then mixed with the substrate (0.02-0.20 mol) andtransferred into a stainless-steel Parr reactor (75 mL or 300 mL)equipped with a magnetic stir bar. The reactor was closed, taken out ofthe glovebox, tightened and connected to a hydrogen tank. After purgingthe line, the reactor was pressurized to 725 psi (50 Bar) anddisconnected from the H₂ source (with the exception of reactionsconducted in the 300 mL reactor using 0.2 mol of substrate). Then, thereactor was placed in an oil bath preheated to 40° C. At the end of thereaction time, the reactor was moved into a cold water bath for 5 minand depressurized.

The results of the above hydrogenation experiments demonstrate that anoutstanding ethanol dehydrogenation catalyst might also have superiorefficiency in hydrogenation of substrates with polar C═X bonds. Catalyst7 is particularly successful for the reduction of alkanoates, giving anunprecedented 20 000 turnovers in 16 h for ethyl acetate and 18 800turnovers in 18 h for methyl hexanoate, both at 40° C. The best turnovernumber (TON) reported to date for this type of substrate was 7100 in 18h at 100° C. for methyl hexanoate, using a ruthenium dimer{RuH(CO)[N(C₂H₄PiPr₂)₂]}₂ (Spasyuk, D., Smith, S., Gusev, D. G. Angew.Chem., Int. Ed. 2012, 51, 2772-2775). For another comparison, the bestFirmenich catalyst, RuCl₂(H₂NC₂H₄PPh₂)₂, would theoretically need 27 hto produce 18 600 turnovers for methyl octanoate at 100° C., on thebasis of the reported TOF=688 h⁻¹ over a 2.5 h reaction time. (UnitedStates patent application publication No. US 2010-280273). Complex 7 isalso a competent imine hydrogenation catalyst, giving a particularlyhigh TON=50 000 for N-benzylaniline.

Example 22—Synthesis of μ_(N)-(RuH(CO)[PyCH₂N(CH₂)₂P(iPrh)₂]₂

A mixture of diethyl ether and THF (2:1, 15 mL) was added to a mixtureof Complex 3 (640 mg, 1.53 mmol) and tBuOK (172 mg, 1.53 mmol) and theresulting solution was stirred for 5 min. During this time the colorchanged from yellow to dark purple, then to dark green. The productsolution was placed into a freezer at −18 degrees Celsius for 15 min andsubsequently filtered through a glass frit. The solvent was removedunder vacuum to yield 532 mg (91%) of a mixture of two isomers ofComplex 4. The major isomer was obtained in a pure form as a brightyellow solid (340 mg, 58%) after recrystallization of the mixture from 5mL of toluene at 60° C.

³¹P {¹H} NMR ([D2]DCM) δ=93.80 (s), 90.25 (s). ¹H{³¹P} NMR ([D2]DCM)δ=9.01 (dd, J=5.5, 0.8 Hz, 1H; Py), 8.40 (d, J=5.4 Hz, 1H; Py), 7.15(td, J=7.7, 1.6 Hz, 1H; Py), 7.10 (td, J=7.7, 1.7 Hz, 1H; Py), 6.86 (t,J=6.5 Hz, 2H; Py), 6.46 (d, J=7.9 Hz, 1H; Py), 6.27 (d, J=8.0 Hz, 1H;Py), 4.50 (d, J=18.0 Hz, 1H; CH₂), 4.15 (d, J=17.9 Hz, 1H; CH₂), 4.05(dd, J=18.0, 1.6 Hz, 1H, CH₂), 3.55-3.24 (m, 3H), 3.11 (dd, J=11.8, 5.3Hz, 1H; CH₂), 2.95-2.78 (m, 2H), 2.61-2.45 (m, 1H), 2.37-2.17 (m, 2H),2.03 (dd, J=−13.4, 3.8 Hz, 1H; CH₂), 1.91 (hept, J=7.2 Hz, 1H; CH), 1.74(td, J=14.1, 5.6 Hz, 1H; CH₂), 1.53-1.43 (dd overlapped with d, 1H;CH₂), 1.44 (d overlapped with dd, J=7.6 Hz, 3H; CH₃), 1.38 (d, J=2.4 Hz,3H; CH₃), 1.35 (d, J=1.8 Hz, 3H; CH₃), 1.31 (d, J=6.9 Hz, 3H; CH₃), 1.16(d, J=6.8 Hz, 3H; CH₃), 1.05 (d, J=6.9 Hz, 6H; CH₃), 1.00 (d, J=6.8 Hz,3H; CH₃), −12.45 (s, 1H; RuH), −13.68 (s, 1H; RuH). ¹³C {¹H} NMR([D6]Benzene) δ=209.64 (d. J(CP)=17.0 Hz, 1C; CO), 207.30 (d, J(CP)=12.4Hz, 1C; CO), 169.03 (d, J(CP)=2.2 Hz, 1C; Py), 168.09 (s, 1C; Py),155.64 (s, 1C; Py), 151.26 (s, 1C; Py), 134.92 (s, 1C; Py), 134.51 (s,1C; Py), 121.37 (d, J(CP)=2.4 Hz, 1C; Py), 120.97 (s, 1C; Py), 118.09(s, 1C; Py), 117.65 (s, 1C; Py), 74.01 (d, J(CP)=2.6 Hz, 1C; PyCH₂),71.36 (m, 2C; PyCH₂+NCH₂), 69.73 (s, 1C; NCH₂), 33.66 (d, J(CP)=22.8 Hz,1C; CH), 31.68 (d, J(CP)=11.5 Hz, 1C; CH), 29.39 (d, J(CP)=4.1 Hz, 1C;CH₂), 29.11 (s, 1C; CH₂), 26.64 (d, J(CP)=29.2 Hz, 1C; CH), 25.11 (d,J(CP)=32.6 Hz, 1C, CH), 21.60 (d, J(CP)=4.1 Hz, 1C; CH₃), 21.47 (d,J(CP)=5.1 Hz, 1C; CH₃), 21.07 (d, J(CP)=7.3 Hz, 1C; CH₃), 20.94 (d,J(CP)=5.0 Hz, 1C; CH₃), 19.77 (s, 1C; CH₃), 19.41 (s, 1C; CH₃), 17.69(d, J(CP)=3.2 Hz, 1C; CH₃), 17.59 (d, J(CP)=2.9 Hz, 1C; CH₃). Anal.Calcd for (C₁₅H₂₅N₂RuOP)₂: C, 47.23; H, 6.61; N, 7.34. Found: C, 46.95;H, 6.53; N, 7.15.

Example 23—Crystal Structure Determination of Complex 7

Single crystals of complex 7 were grown by slow diffusion of hexanesinto a saturated solution in dichloromethane. The data was collected ona Bruker Microstar™ generator equipped with Helios optics, a KappaNonius™ goniometer, and a Platinum-135 detector. Cell refinement anddata reduction were done using SAINT™ (SAINT (1999) Release 6.06;Integration Software for Single Crystal Data. Bruker AXS Inc., Madison,Wis., USA.) An empirical absorption correction, based on the multiplemeasurements of equivalent reflections, was applied using the programSADABS™ (Sheldrick, G. M. (1999). SADABS, Bruker Area DetectorAbsorption Corrections. Bruker AXS Inc., Madison, Wis., USA.). The spacegroup was confirmed by XPREP routine of SHELXTL (XPREP (1997) Release5.10; X-ray data Preparation and Reciprocal space Exploration Program,Bruker AXS Inc., Madison, Wis., USA.; SHELXTL (1997) Release 5.10; TheComplete Software Package for Single Crystal Structure Determination,Bruker AXS Inc., Madison, Wis., USA.). The structure was solved bydirect-methods and refined by full-matrix least squares and differenceFourier techniques with SHELX-97 as a part of LinXTL tool box(Sheldrick, G. M. (1997). SHELXS97, Program for the Solution of CrystalStructures. Univ. Of Gottingen, Germany; Sheldrick, G. M. (1997).SHELXL97, Program for the Refinement of Crystal Structures. Universityof Gottingen, Germany.). All non-hydrogen atoms were refined withanisotropic displacement parameters. Hydrogen atoms were set incalculated positions and refined as riding atoms with a common thermalparameter, except those of the NH moiety and hydrides, which werepositioned from residual peaks in the difference Fourier map. Thecollection parameters and bond distances and angles can be found intables 5 and 6, respectively.

TABLE 6 Crystal Data Collection and Refinement Parameters for Complex 7chemical formula C₃₈H₃₆Cl₂N₂P₂Ru crystal colour Yellow Fw; F(000)754.60; 772 T (K) 150 wavelength (Å) 1.54178 space group P-1 a (Å)10.5195(3) b (Å) 13.2513(3) c (Å) 16.3644(4) α(deg) 68.972(1) β(deg)88.622(1) γ(deg) 67.031(1) Z 2.00 V (Å³) 1942.49(9) ρ_(calcd) (g · cm⁻³)1.290 μ (mm⁻¹) 5.511 θ range (deg); completeness 4.61-69.76; 0.971collectedreflectious; R_(σ) 30435; 0.0328 unique reflections; R_(int)30435; 0.0386 R1^(a); wR2^(b) [I > 2σ(I)] 0.0297; 0.0765 R1; wR2 [alldata] 0.0299; 0.0767 GOF 0.975 largest diff peak and hole 1.054 and−0.464

TABLE 7 Selected Bond Distances (Å) and Angles (deg) for Complex 7 7Ru1—N1 2.143(2) Ru1—N2 2.160(2) Ru1—P1 2.302(5) Ru1—P2 2.3305(4) Ru1—Cl22.4093(4) Ru1—Cl1 2.4138(4) N1—Ru1—N2 75.46(6) N1—Ru1—P1 83.43(5)N2—Ru1—P1 158.00(4) N2—Ru1—P2 97.93(4) P1—Ru1—P2 103.56(2) P1—Ru1—Cl295.6(2)

All publications, patents and patent applications mentioned in thisSpecification are indicative of the level of skill of those skilled inthe art to which this invention pertains and are herein incorporated byreference to the same extent as if each individual publication, patent,or patent applications was specifically and individually indicated to beincorporated by reference.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. A complex of Formula II or III[M(LNN′)Z_(a)]  (II)μ^(N)[M(LNN′)Z_(a)]₂  (III) wherein: each Z is independently a hydrogenor halogen atom, a C₁-C₆ alkyl, a hydroxyl, or a C₁-C₆ alkoxy, anitrosyl (NO) group, CO, PMe₃, PPh₃, or CNR, wherein R is an alkyl or anaryl; M is Ru or Os; a is 2 or 3; each LNN′ is a coordinated ligand thatis a compound according to:

wherein L is a phosphine (PR¹R²); the dotted lines simultaneously orindependently represent single or double bonds, wherein when a singlebond joins the carbon atom or atoms bound to R⁴ or R⁵ or both, R⁴ or R⁵or both are additionally bound to an H; R¹ and R² are each independentlyH, or a C₁-C₂₀ linear alkyl, a C₃-C₈ cycloalkyl, or a C₅-C₂₀ aryl, eachof which is optionally substituted; R³ is H; R⁴ is H; R⁵ is H; each X isindependently H, a linear C₃-C₈ alkyl, a branched C₃-C₈ alkyl, a cyclicC₃-C₈ alkyl, a C₃-C₈ alkenyl, or a C₅-C₈ aryl, each of which isoptionally substituted, or OR, F, CI, Br, I or NR₂; or when takentogether, two of the X groups together form an optionally substitutedsaturated ring, partially saturated ring, aromatic ring, orheteroaromatic ring; R is H, a C₁-C₂₀ linear alkyl, a C₃-C₂₀ branchedalkyl, a C₃-C₈ cycloalkyl, or a C₅-C₈ aryl, each of which may beoptionally substituted; each n and m is independently 1 or 2; q is 0 or1; and μ^(N) indicates that each LNN′ ligand in the complex of Formula(III) includes a nitrogen atom that bridges two M atoms.
 2. The complexof claim 1, wherein in the compound is:


3. The complex of claim 1, wherein LNN′ is


4. The complex of claim 1 which has the structure of any one of


5. A process for hydrogenation of a substrate comprising treating thesubstrate with a catalytic amount of a complex of Formula II or III[M(LNN′)Z_(a)]  (II)μ^(N)[M(LNN′)Z_(a)]₂  (III) according to claim 1 in the presence ofmolecular hydrogen, wherein the hydrogenation is performed at atemperature in a range from 40° C. to 100° C. for a time in a range of 1to 22 hours, and under 50 Bar pressure.
 6. The process of claim 5,wherein the substrate comprises at least one ester; and/or wherein theprocess proceeds in the presence of molecular hydrogen according to oneof the following schemes

wherein G₁ and G₂, simultaneously or independently, represent a linearC₁-C₄₀ or branched or cyclic C₃-C₄₀ alkyl, alkenyl or aromatic group,any of which may be optionally substituted.
 7. The process of claim 5,wherein the substrate and product pair of the hydrogenation reactioncomprises: Hydrogenation Substrate Product ester alcohol lactone diol.


8. The process of claim 5, which is a solvent-free process.
 9. A processfor producing ethyl acetate comprising treating ethanol with a catalyticamount of a complex of Formula II or III[M(LNN′)Z_(a)]  (II)μ^(N)[M(LNN′)Z_(a)]₂  (III) according to claim 1.